Doubling isn't doubling
Run the honest arithmetic. Three players left; prizes 50/30/20; stacks 50%, 30%, 20% of the chips. The SHORT stack's prize equity is about 28.9% of the pool. Now let it double ALL the way through the chip leader — 20% of the chips becomes 40%. Prize equity after: about 35.4%. Chips +100%, money +23% — the missing three-quarters was paid to everyone who gets to survive you. That is ICM, the Independent Chip Model: chips you win are worth less than chips you lose. Near big pay jumps it reprices everything: calls need MORE equity than raw pot odds, folds gain a subsidy, and the big stack's threats are worth more than their cards.